The present invention relates to an apparatus for longitudinally and transversely trimming articles moldingly formed on the plastic sheet.
Various articles are formed by feeding a heated and softened thermoplastic web between a pair of male and female dies which are normally separated and by bringing said dies engaged together. Said dies may be subjected to raised or reduced pressure as occasion demands. Rectangular articles such as bath tubs, refrigerator inner rooms and the like have been manufactured according to such method. For instance, the freezing compartment and the cooling compartment of the refrigerator, the former being smaller in general than the latter, are preferably formed by one shot of the forming machine operation for the convenience of assembly.
The unnecessary portion of the plastic sheet surrounding the formed articles must be trimmed. Conventionally, a set of upper and lower frames, each comprising four or more blades so arranged as to correspond to the four or more lines of the plastic sheet to be severed have been used so that transverse and longitudinal trimmings are made in one shot by relatively moving said set of frame blades in a vertical direction to engage with each other. According to such conventional trimming method, the cut-off waste portion of the plastic sheet is in one piece like a picture frame held by a pair of clamp link chains along opposite side edges thereof so as to efficiently recover much of the waste.
According to such conventional trimming device, however, every time a size of the article to be formed is varied, the set of trimming frame blades must be exchanged which necessitates many sets of blades of various sizes to be stored, which is space and time consuming. When the trimming device is combined with the moldingly forming machine, which is in turn usually combined with an extruder feeding plastic web thereto, so as to be intermittently operable in synchronized relation therewith, said forming machine and further said extruder if it is combined therewith must be stopped during such time consuming blade exchange work.